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The present invention concerns the use of catheters in the field of interventional neuroradiology. In particular, this invention pertains to microcatheters provided with auxiliary guide structures to permit safe navigation of the catheter within the intracranial vessels for embolization of high flow vascular lesions.
Microcatheter technology has advanced from the 1980""s to the point that a microcatheter is now commonly used in the treatment of vascular lesions of the central nervous system. Microcatheters are low profile catheters used to treat strokes, cerebral aneurysms, fistulas, arterial venous malformations, and other areas by occluding the pathologic vascular abnormality through an endovascular approach utilizing selective deposition of coils, particles, balloons, or liquid adhesives. Such microcatheters can also be used in other areas of the body.
In these delicate procedures, a major difficulty involves steering the catheter through the tortuous bifurcations of the cerebral arteries to navigate it to the site of treatment. Catheter steering difficulties often add hours of time and complications to the procedure making it impractical to treat some areas of the brain. The ability to steer the catheter precisely and quickly is essential for effective catheterizations with minimal risks.
Endovascular treatment of cerebral vascular lesions employs one of two classes of microcatheter, either a flow directed microcatheter or a guidewire directed microcatheter. Flow directed microcatheters typically have a curve steamed in the tip of the microcatheter and are advanced through the vessel based on the amount of blood flow, assisted by externally advancing the catheter, sometimes from a small guidewire. In some cerebral vascular pathologies, a flow directed microcatheter is unable to reach its target, particularly in those areas with slower flow. A guidewire directed microcatheter, on the other hand, is advanced based on catheterization using a micro-guidewire and pushing the catheter distally. This increases the risk of vessel perforation by the guidewire and is often limited by an inability to push the catheter around numerous turns.
As used in the prior art, a guide catheter is first advanced from the femoral artery by a percutaneous method, terminating in a carotid or vertebral artery. A microcatheter is then advanced through the guide catheter into the cervical and cerebral vasculature. The placement of such a microcatheter is accomplished either by use of a guidewire or by taking advantage of hemodynamics. Each of these conventional methodologies has drawbacks. The guidewire directed microcatheter risks puncturing a vessel or aneurysm with significant hemorrhagic consequences intracranially. The flow directed microcatheter frequently lacks control directionality. New guidewires may now be used with flow directed microcatheters, however, this reintroduces the risks associated with the use of a guidewire and also raises the possibility of puncturing the wall of the flow directed soft microcatheter. Delivery of the greatest variety of embolic agents is usually possible only through a guidewire directed catheter. A more limited selection of embolization materials can be delivered through a flow directed microcatheter due to its suppleness.
What is needed, then, is a microcatheter than can be quickly and precisely guided through the vascular system for treatment of cerebral vascular lesions, with a reduced risk of vessel perforation.
The microcatheter of the present invention combines a catheter body with a hemodynamic guide structure attached to the catheter body proximal to its distal orifice. The guide structure is wing-shaped to take advantage of Bernoulli""s principal and the kinetic energy of laminar blood flow around the catheter. The wing provides hemodynamic lift to move the catheter tip toward vessel walls and into a vessel bifurcation branch.
The wing-shaped guide structure generates lift from hemodynamic flow similar to that commonly employed by wings on conventional aircraft. This lift can be used to direct the tip of the microcatheter into a branch of a primary or parent vessel, including one that has an acute reverse orientation. By controlling the proximal external hub portion of the catheter, the wing can be oriented to course along the desired wall of the catheterized vessel until the orifice of the branching vessel is located, thereby permitting the catheter to be further advanced into the branching vessel. The catheter of this invention permits rapid and safe catheterization of cerebral vessels without the use of a guidewire and without tip stem curvature. Multiple embolic agents can be used with the catheter and it is particularly well suited for the use of liquid adhesives. It can be employed in highflow vessels, and the microcatheter is also functional in cerebral vessels of normal flow.
The size of the wing-shaped. guide structure is operational on the scale commonly encountered in cerebral microcatheters. It has particular applicability in the treatment of cerebral arterial venous malformations, especially using liquid adhesives.
Thus, the present invention provides a catheter device for therapeutic and diagnostic use within a human vascular system. The catheter has a cylindrical catheter body formed around a lumen, with a hub located at a proximal end of the catheter body, and a tip located at a distal end of the body. A guide structure is connected to the catheter body proximate the tip, with the guide structure having a wing shape that provides hemodynamic lift in response to laminar blood flow around the catheter. The wing shape of the guide structure tapers down from a leading edge to a trailing edge, with the leading edge facing the catheter tip so that when the catheter is positioned inside a vessel wall of the vascular system and oriented in a downstream direction, the lift created by the laminar blood flow biases the catheter tip toward the vessel wall. Preferably, the distal end of the catheter body comprises a flexible material so that the catheter tip can deflect and move towards the vessel wall in response to the hemodynamic lift. An intermediate section of the catheter body between the hub and the tip provides a semi-rigid control connection whereby pushing, pulling, and rotation of the hub produces a corresponding movement of the catheter tip.